Glucose transport into everted sacs of the small intestine of mice.

The Na(+)-glucose cotransporter is a key transport protein that is responsible for absorbing Na(+) and glucose from the luminal contents of the small intestine and reabsorption by the proximal straight tubule of the nephron. Robert K. Crane originally described the cellular model of absorption of Na(+) and glucose by a "cotransport process" in 1960. Over the past 50+ yr, numerous groups have tested and verified Crane's hypothesis. Eventually, Wright and colleagues cloned the Na(+)-glucose cotransporter (SGLT1; the product of the SLC5A1 gene) in 1987. This article provides a "hands-on" laboratory exercise using the everted mouse jejunal preparation (everted sac) that allows students to investigate various components of the Na(+)-glucose cotransport absorptive cell model (e.g., Na(+) dependence of SGLT1, inhibition of SGLT1, and inhibition of Na(+)-K(+)-ATPase). Additionally, the laboratory exercise includes a case-based study of glucose-galactose malabsorption in which the students conduct an internet search and participate in a small-group discussion during the laboratory period to better understand the basic principles and functions of the Na(+)-glucose absorptive process of the small intestine. This laboratory exercise was introduced into the second-year undergraduate physiology curriculum in 2008, and >850 physiology students have participated in this laboratory exercise. The students have produced very robust and reproducible data that clearly illustrate the theory of the cellular model for Na(+)-glucose absorption by the jejunum.